A new study finds that processed products such as bologna and hot dogs, and red meat in general can increase your risk of type 2 diabetes by almost half, and that by getting your protein from other rich sources such as nuts, whole grains and dairy low in fat, it will actually have the reverse effect.

A daily serving of 50 grams of processed meat, equivalent to one hot dog or sausage or two slices of bacon, was associated with a 51% increased risk of diabetes.

Researchers from Harvard looked at 20 years of data from men in the Health Professionals Follow-Up Study, 28 years of data from women in the Nurses’ Health Study I, and 14 years of data from women in the Nurses’ Health Study II, which involved more than 200,000 participants in all and a total of 442,101 people’s history were analyzed, including 28,228 who developed diabetes while participating in one of the studies.

After adjusting for lifestyle and dietary risk factors, the researchers determined that a daily 100 gram serving (about the size of a deck of cards) of unprocessed red meat was associated with a 19% increased risk for type 2 diabetes.

Among people who ate one daily serving of red meat, substituting one serving of whole grains per day reduced the risk of diabetes by 23%. Substituting nuts resulted in a 21% lower risk, and substituting a low-fat dairy product, a 17% lower risk.

Frank Hu, a professor of nutrition and epidemiology, said in a Harvard news release:

“Clearly, the results from this study have huge public health implications given the rising type 2 diabetes epidemic and increasing consumption of red meats worldwide. The good news is that such troubling risk factors can be offset by swapping red meat for a healthier protein.”

United States food guidelines that include red meats in the protein foods group along with fish, nuts, beans and poultry should be revised to distinguish red meat from the healthier protein sources, the authors also commented.

What about links to other disease? A recent National Institutes of Health AARP study of more than a half million older Americans concluded that people who ate the most red meat and processed meat over a 10-year-period were likely to die sooner than those who ate smaller amounts. Those who ate about 4 ounces of red meat a day were more likely to die of cancer or heart disease than those who ate the least, about a half-ounce a day. Epidemiologists classified the increased risk as “modest” in the study.

The meat industry contends there is no link between red meat, processed meats, and cancer, and says that lean red meat fits into a heart-healthy diet.

A meat industry spokeswoman criticized the design of the NIH-AARP study, saying that studies that rely on participants to recall what foods they eat cannot prove cause and effect.

Janet Riley, a senior vice president of the American Meat Institute said:

“Many of these suggestions could be nothing more than statistical noise.”